Does Induction Time of Mild Hypothermia Influence the Survival Duration of Septic Rats?

Mild induced hypothermia and coagulation and platelet function in patients with septic shock: Secondary outcome of a randomized trial

Coagulation abnormalities and microthrombi contribute to septic shock, but the impact of body temperature regulation on coagulation in patients with sepsis is unknown. We tested the hypothesis that mild induced hypothermia reduces coagulation and platelet aggregation in patients with septic shock. Secondary analysis of randomized controlled trial. Adult patients with septic shock who required mechanical ventilation from eight intensive care units in Denmark were randomly assigned to mild induced hypothermia for 24 h or routine thermal management. Viscoelastography and platelet aggregation were assessed at trial inclusion, after 12 h of thermal management, and 24 h after inclusion. A total of 326 patients were randomized to mild induced hypothermia (n = 163) or routine thermal management (n = 163). Mild induced hypothermia slightly prolonged activated partial thromboplastin time and thrombus initiation time (R time 8.0 min [interquartile range, IQR 6.6-11.1] vs. 7.2 min [IQR 5.8-9.2]; p = .004) and marginally inhibited thrombus propagation (angle 68° [IQR 59-73] vs. 71° [IQR 63-75]; p = .014). The effect was also present after 24 h. Clot strength remained unaffected (MA 71 mm [IQR 66-76] with mild induced hypothermia vs. 72 mm (65-77) with routine thermal management, p = .9). The proportion of patients with hyperfibrinolysis was not affected (0.7% vs. 3.3%; p = .19), but the proportion of patients with no fibrinolysis was high in the mild hypothermia group (8.8% vs. 40.4%; p < .001). The mild induced hypothermia group had lower platelet aggregation: ASPI 85U (IQR 50-113) versus 109U (IQR 74-148, p < .001), ADP 61U (IQR 40-83) versus 79 U (IQR 54-101, p < .001), TRAP 108 (IQR 83-154) versus 119 (IQR 94-146, p = .042) and COL 50U (IQR 34-66) versus 67U (IQR 46-92, p < .001). In patients with septic shock, mild induced hypothermia slightly impaired clot initiation, but did not change clot strength. Platelet aggregation was slightly impaired. The effect of mild induced hypothermia on viscoelastography and platelet aggregation was however not in a range that would have clinical implications. We did observe a substantial reduction in fibrinolysis.

Sepsis-Induced Myocardial Dysfunction (SIMD): the Pathophysiological Mechanisms and Therapeutic Strategies Targeting Mitochondria

Sepsis is a lethal syndrome with multiple organ failure caused by an inappropriate host response to infection. Cardiac dysfunction is one of the important complications of sepsis, termed sepsis-induced myocardial dysfunction (SIMD), which is characterized by systolic and diastolic dysfunction of both sides of the heart. Mechanisms that contribute to SIMD include an excessive inflammatory response, altered circulatory, microvascular status, nitric oxide (NO) synthesis impairment, endothelial dysfunction, disorders of calcium regulation, cardiac autophagy anomaly, autonomic nervous system dysregulation, metabolic reprogramming, and mitochondrial dysfunction. The role of mitochondrial dysfunction, which is characterized by structural abnormalities, increased oxidative stress, abnormal opening of the mitochondrial permeability transition pore (mPTP), mitochondrial uncoupling, and disordered quality control systems, has been gaining increasing attention as a central player in the pathophysiology of SIMD. The disruption of homeostasis within the organism induced by mitochondrial dysfunction may also be an important aspect of SIMD development. In addition, an emerging therapy strategy targeting mitochondria, namely, metabolic resuscitation, seems promising. The current review briefly introduces the mechanism of SIMD, highlights how mitochondrial dysfunction contributes to SIMD, and discusses the role of metabolic resuscitation in the treatment of SIMD.

Staying Cool in Space: A Review of Therapeutic Hypothermia and Potential Application for Space Medicine

Despite rigorous health screenings, medical incidents during spaceflight missions cannot be avoided. With long-duration exploration flights on the rise, the likelihood of critical medical conditions with no suitable treatment on board will increase. Therapeutic hypothermia (TH) could serve as a bridge treatment in space prolonging survival and reducing neurological damage in ischemic conditions such as stroke and cardiac arrest. We conducted a review of published studies to determine the potential and challenges of TH in space based on its physiological effects, the cooling methods available, and clinical evidence on Earth. Currently, investigators have found that application of low normothermia leads to better outcomes than mild hypothermia. Data on the impact of hypothermia on a favorable neurological outcome are inconclusive due to lack of standardized protocols across hospitals and the heterogeneity of medical conditions. Adverse effects with systemic cooling are widely reported, and could be reduced through selective brain cooling and pharmacological cooling, promising techniques that currently lack clinical evidence. We hypothesize that TH has the potential for application as supportive treatment for multiple medical conditions in space and recommend further investigation of the concept in feasibility studies.

Study of thermo-regulation as a worsening marker of experimental sepsis in an animal model

Objective:

to analyze variations in body temperature and in plasma nitrate and lactate concentrations in rats submitted to the experimental sepsis model.

Method:

a total of 40 rats divided equally into five groups. The induction of endotoxemia was performed with intravenous administration of lipopolysaccharide, 0.5 mg/Kg, 1.5 mg/Kg, 3.0 mg/Kg, and 10 mg/Kg, respectively. The control group received 0.5 mL of saline solution. The experiment lasted six hours, with evaluations performed at 0 (baseline data), 2^nd, 4^th, and 6^thhours.

Results:

The animals that received doses up to 3.0 mg/kg showed a significant increase in body temperature compared to the group with 10 mg/kg, which showed a decrease in these values. The increase in plasma nitrate and lactate concentrations in the groups with lipopolysaccharide was significantly higher than in the group that received the saline solution and was correlated with the increase in body temperature.

Conclusion:

the variations in body temperature observed in this study showed the dose-dependent effect of lipopolysaccharide and were correlated with the increase in the concentrations of nitrate and plasma lactate biomarkers. The implications of this study are the importance of monitoring body temperature, together with the assessment of these pathophysiological markers, which suggest worsening in the prognosis of sepsis.

Induced hypothermia in patients with septic shock and respiratory failure (CASS): a randomised, controlled, open-label trial

BACKGROUND

Animal models of serious infection suggest that 24 h of induced hypothermia improves circulatory and respiratory function and reduces mortality. We tested the hypothesis that a reduction of core temperature to 32-34°C attenuates organ dysfunction and reduces mortality in ventilator-dependent patients with septic shock.

METHODS

In this randomised, controlled, open-label trial, we recruited patients from ten intensive care units (ICUs) in three countries in Europe and North America. Inclusion criteria for patients with severe sepsis or septic shock were a mean arterial pressure of less than 70 mm Hg, mechanical ventilation in an ICU, age at least 50 years, predicted length of stay in the ICU at least 24 h, and recruitment into the study within 6 h of fulfilling inclusion criteria. Exclusion criteria were uncontrolled bleeding, clinically important bleeding disorder, recent open surgery, pregnancy or breastfeeding, or involuntary psychiatric admission. We randomly allocated patients 1:1 (with variable block sizes ranging from four to eight; stratified by predictors of mortality, age, Acute Physiology and Chronic Health Evaluation II score, and study site) to routine thermal management or 24 h of induced hypothermia (target 32-34°C) followed by 48 h of normothermia (36-38°C). The primary endpoint was 30 day all-cause mortality in the modified intention-to-treat population (all randomly allocated patients except those for whom consent was withdrawn or who were discovered to meet an exclusion criterion after randomisation but before receiving the trial intervention). Patients and health-care professionals giving the intervention were not masked to treatment allocation, but assessors of the primary outcome were. This trial is registered with ClinicalTrials.gov, number NCT01455116.

FINDINGS

Between Nov 1, 2011, and Nov 4, 2016, we screened 5695 patients. After recruitment of 436 of the planned 560 participants, the trial was terminated for futility (220 [50%] randomly allocated to hypothermia and 216 [50%] to routine thermal management). In the hypothermia group, 96 (44·2%) of 217 died within 30 days versus 77 (35·8%) of 215 in the routine thermal management group (difference 8·4% [95% CI -0·8 to 17·6]; relative risk 1·2 [1·0-1·6]; p=0·07]).

INTERPRETATION

Among patients with septic shock and ventilator-dependent respiratory failure, induced hypothermia does not reduce mortality. Induced hypothermia should not be used in patients with septic shock.

FUNDING

Trygfonden, Lundbeckfonden, and the Danish National Research Foundation.

A Brief Period of Hypothermia Induced by Total Liquid Ventilation Decreases End-Organ Damage and Multiorgan Failure Induced by Aortic Cross-Clamping

BACKGROUND

In animal models, whole-body cooling reduces end-organ injury after cardiac arrest and other hypoperfusion states. The benefits of cooling in humans, however, are uncertain, possibly because detrimental effects of prolonged cooling may offset any potential benefit. Total liquid ventilation (TLV) provides both ultrafast cooling and rewarming. In previous reports, ultrafast cooling with TLV potently reduced neurological injury after experimental cardiac arrest in animals. We hypothesized that a brief period of rapid cooling and rewarming via TLV could also mitigate multiorgan failure (MOF) after ischemia-reperfusion induced by aortic cross-clamping.

METHODS

Anesthetized rabbits were submitted to 30 minutes of supraceliac aortic cross-clamping followed by 300 minutes of reperfusion. They were allocated either to a normothermic procedure with conventional ventilation (control group) or to hypothermic TLV (33°C) before, during, and after cross-clamping (pre-clamp, per-clamp, and post-clamp groups, respectively). In all TLV groups, hypothermia was maintained for 75 minutes and switched to a rewarming mode before resumption to conventional mechanical ventilation. End points included cardiovascular, renal, liver, and inflammatory parameters measured 300 minutes after reperfusion.

RESULTS

In the normothermic (control) group, ischemia-reperfusion injury produced evidence of MOF including severe vasoplegia, low cardiac output, acute kidney injury, and liver failure. In the TLV group, we observed gradual improvements in cardiac output in post-clamp, per-clamp, and pre-clamp groups versus control (53 ± 8, 64 ± 12, and 90 ± 24 vs 36 ± 23 mL/min/kg after 300 minutes of reperfusion, respectively). Liver biomarker levels were also lower in pre-clamp and per-clamp groups versus control. However, acute kidney injury was prevented in pre-clamp, and to a limited extent in per-clamp groups, but not in the post-clamp group. For instance, creatinine clearance was 4.8 ± 3.1 and 0.5 ± 0.6 mL/kg/min at the end of the follow-up in pre-clamp versus control animals (P = .0004). Histological examinations of the heart, kidney, liver, and jejunum in TLV and control groups also demonstrated reduced injury with TLV.

CONCLUSIONS

A brief period of ultrafast cooling with TLV followed by rapid rewarming attenuated biochemical and histological markers of MOF after aortic cross-clamping. Cardiovascular and liver dysfunctions were limited by a brief period of hypothermic TLV, even when started after reperfusion. Conversely, acute kidney injury was limited only when hypothermia was started before reperfusion. Further work is needed to determine the clinical significance of our results and to identify the optimal duration and timing of TLV-induced hypothermia for end-organ protection in hypoperfusion states.

Mild hypothermia ameliorates muscle wasting in septic rats associated with hypothalamic AMPK-induced autophagy and neuropeptides

Sepsis, always developing muscle wasting, contributes to serious complications and mortality. Mild hypothermia has been reported to have protective effects on the prognosis of septic patients. However, the underlying mechanisms remain unclear. We therefore hypothesized that mild hypothermia could ameliorate muscle wasting during sepsis and whether it was associated with hypothalamus AMPK-induced autophagy and neuropeptides. Adult male Sprague-Dawley rats were intraperitoneally injected with lipopolysaccharide (LPS) (5 mg/kg) or saline. Mild hypothermia was instantly induced at 33 °C for 3h after LPS injected. Meanwhile, the control and sepsis groups were simultaneously placed on the thermal mattress to maintain the a normal temperature in control group whatever the changes induced by anesthesia. Twenty-four hours after injection, skeletal muscle and hypothalamus tissues were obtained. Muscle wasting was measured by the mRNA expression of two muscle atrophic genes, muscle ring finger 1 (MuRF-1) and muscle atrophy F-box (MAFbx), as well as 3-methylhistidine (3-MH) and tyrosine release. Hypothalamic AMPK-induced autophagy markers and neuropeptides expression were also detected. Results showed that LPS administration significantly decreased hypothalamic AMPK-induced autophagy together with muscle wasting. Also, increased hypothalamic neuropeptides, proopiomelanocortin (POMC), cocaine and amphetamine-related transcript (CART) and neuro-peptides Y (NPY) and decreased agouti-related protein (AgRP) were observed. Mild hypothermia significantly increased hypothalamic AMPK-induced autophagy and ameliorated LPS-induced muscle wasting, and attenuated the alteration of neuropeptides, POMC, CART and NPY. In conclusion, mild hypothermia could alleviate muscle wasting by LPS injection, which was associated with reversing the level of hypothalamic AMPK-induced autophagy and the alteration of neuropeptides. These results suggested that mild hypothermia could be a potential treatment concept and a novel mechanism in management of muscle wasting in critically ill patients.

Acute kidney injury and inflammatory response of sepsis following cecal ligation and puncture in d-galactose-induced aging rats

Background

Recently, the d-galactose (d-gal)-induced mimetic aging rat model has been widely used in studies of age-associated diseases, which have shown that chronic d-gal exposure induces premature aging similar to natural aging in rats. With the increasing rate of sepsis in the geriatric population, an easy-access animal model for preclinical studies of elderly sepsis is urgently needed. This study investigates whether a sepsis model that is established in d-gal-induced aging rats can serve as a suitable model for preclinical studies of elderly patients with sepsis.

Objective

To investigate the acute kidney injury (AKI) and inflammatory response of sepsis following cecal ligation and puncture (CLP) in d-gal-induced aging rats.

Methods

Twelve-week-old male Sprague Dawley rats were divided into low-dose d-gal (L d-gal, 125 mg/kg/d), high-dose d-gal (H d-gal, 500 mg/kg/d), and control groups. After daily subcutaneous injection of d-gal for 6 weeks, the CLP method was used to establish a sepsis model.

Results

The mortality was 73.3%, 40%, and 33.3% in the H d-gal, L d-gal, and control groups, respectively. Blood urea nitrogen, creatinine, plasma neutrophil gelatinase-associated lipocalin, interleukin-6, interleukin-10, and tumor necrosis factor-α were markedly increased in the H d-gal group after establishment of the sepsis model (H d-gal vs control, P<0.05 at 12 h and 24 h post-CLP). The rate of severe AKI (RIFLE-F) at 24 h post-CLP was 43% for both the control and L d-gal groups and 80% for the H d-gal group.

Conclusion

High-dose- d-gal-induced aging rats are more likely to die from sepsis than are young rats, and probably this is associated with increased severity of septic AKI and an increased inflammatory response. Therefore, use of the high-dose- d-gal-induced aging rat model of sepsis for preclinical studies can provide more useful information for the treatment of sepsis in elderly patients.